On the same $150,000 gross, a worker takes home roughly ₩16,150 more per year in South Korea than in Singapore. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Singapore has very high rent pressure, while South Korea has high rent pressure. That means part of the higher take-home in South Korea can be absorbed by rent if you land in a major city.
Healthcare and pensions go in the opposite direction. Singapore runs a mixed healthcare model — MediSave/MediShield is mandatory for citizens & PRs; expats use private cover. South Korea uses a universal model — National Health Insurance covers almost all residents. The country with lower take-home often shifts costs that the other country leaves to your private budget.
Net-of-everything, a relocation decision should weigh balanced public welfare in Singapore against strong public welfare in South Korea, plus differences in pension capture, social safety nets, and city-level cost of living.